Long-Range Electron Transfer in Zinc-Phthalocyanine-Oligo(Phenylene-ethynylene)-Based Donor-Bridge-Acceptor Dyads

Abstract

In the context of long-range electron transfer for solar energy conversion, we present the synthesis, photophysical, and computational characterization of two new zinc(II) phthalocyanine oligophenylene-ethynylene based donor-bride-acceptor dyads: ZnPc-OPE-AuP(+) and ZnPc-OPE-C(60). A gold(III) porphyrin and a fullerene has been used as electron accepting moieties, and the results have been compared to a previously reported dyad with a tin(IV) dichloride porphyrin as the electron acceptor (Fortage et al. Chem. Commun. 2007, 4629). The results for ZnPc-OPE-AuP(+) indicate a remarkably strong electronic coupling over a distance of more than 3 nm. The electronic coupling is manifested in both the absorption spectrum and an ultrafast rate for photoinduced electron transfer (k(PET) = 1.0 × 10(12) s(-1)). The charge-shifted state in ZnPc-OPE-AuP(+) recombines with a relatively low rate (k(BET) = 1.0 × 10(9) s(-1)). In contrast, the rate for charge transfer in the other dyad, ZnPc-OPE-C(60), is relatively slow (k(PET) = 1.1 × 10(9) s(-1)), while the recombination is very fast (k(BET) ≈ 5 × 10(10) s(-1)). TD-DFT calculations support the hypothesis that the long-lived charge-shifted state of ZnPc-OPE-AuP(+) is due to relaxation of the reduced gold porphyrin from a porphyrin ring based reduction to a gold centered reduction. This is in contrast to the faster recombination in the tin(IV) porphyrin based system (k(BET) = 1.2 × 10(10) s(-1)), where the excess electron is instead delocalized over the porphyrin ring.

Oligo(p‐phenyleneethynylene) (OPE) Molecular Wires: Synthesis and Length Dependence of Photoinduced Charge Transfer in OPEs with Triarylamine and Diaryloxadiazole End Groups

“…An OPE bridge (comprising three phenyl units) was shown to mediate efficient electron transfer between a donor zinc phthalocyanine and acceptors pyrrolidinoC 60 or gold porphyrin with strong electronic coupling over a distance of >30 Å. [16,17] The excited-state dynamics of systems consisting of a zinc tetraphenylporphyrin and a free base tetraphenylporphyrin bridged by longer OPE units have been investigated using ultrafast spectroscopy. [18] UV-Visible absorption studies on OPE wires terminated with dialkylamino donor and cyano, formyl or nitro acceptor groups showed a competition between the extension of the chromophores and a decrease of the ICT upon increasing the number of PE repeat units.…”

Host–guest interaction dictated selective adsorption and fluorescence quenching of a luminescent lightweight metal–organic framework toward liquid explosives

“…Moreover, although the vapor pressure of NE is comparable to that of NM, the quenching efficiency of NE is significantly less because NE molecules have one more -CH 2 -group, which hinders a fast long-range electron transfer between BPNO and NE interactions. 19 Until now, there have been only a few materials reported that could be used for the fluorescence-quenching based vapor detection of NM and NE under ambient conditions, because of their high volatility. 20…”

Long‐Lived, Emissive Excited States in Direct and Amide‐Linked Thienyl‐Substituted RuII Complexes

“…[4,[21][22][23] As expected, it has been shown that both the length and the nature of the linker greatly influence the properties of molecular wire-like electron and energy transfer behavior within these assemblies. [4,14,[24][25][26][27] Previously, we have reported homoleptic Ru II dyads that exhibit long charge-separated state lifetimes resulting from the formation of an excited state comprised of three equilibrating states. [28] We have also reported a series of heteroleptic complexes bearing laminate acceptor ligands that undergo directional photoinduced charge separation to give relatively long lived charge-separated species.…”